1. Field of the Invention
The invention relates to a device for clamping a fluidic component, particularly a nozzle, particularly in the high pressure region. Of particular interest are holders for micro-engineered components, particularly micro-engineered nozzles which are to be produced by micro-engineering. Such nozzles are used for example in nebulizers for producing propellant-free medicinal aerosols used for inhalation.
The aim of the invention is to further improve the clamping of a fluidic component consisting of a wear-resistant, hard, and generally brittle material, and to increase the reliability of the holder.
2. Brief Description of the Prior Art
Micro-engineered nozzles having for example a nozzle aperture of less than 10 μm are described for example in WO 94/07607 and WO 99/16530. The inhalable droplets produced thereby have a mean diameter of about 5 μm, when the pressure of the liquid to be nebulized is from 5 MPa (50 bar) to 40 MPa (400 bar). The nozzles may for example be made from thin sheets of silicon and glass. The external dimensions of the nozzles are in the millimeter range. A typical nozzle consists for example of a cuboid with sides measuring 1.1 mm, 1.5 mm and 2.0 mm, made up of two sheets. Nebulizers for producing propellant-free aerosols in which the device according to the invention for clamping a fluidic component can be used are known from WO 91/14468 or WO 97/12687.
The term fluidic component denotes a component which is exposed to a pressurized fluid, and the pressure is also present inside the component, for example in a nozzle bore. Such a component may be kept pressure-tight for example by pressing into a holder of hard material if the material of the component can withstand mechanical forces without collapsing or deforming to an unacceptable degree. At high pressures, seals of deformable material, e.g. copper, or hard material which can be pressed in with great force are used. In the case of components made of brittle material the known processes for pressure-tight clamping of the component require considerable effort and great care. It is impossible to predict with any reliability the service life of a fluidic component clamped in this way.
U.S. Pat. No. 3,997,111 describes a fluid jet cutting device with which a high-speed fluid jet is produced which is used for cutting, drilling or machining material. The nozzle body is cylindrical and consists e.g. of sapphire or corundum. The setting ring is pressed into an annular recess in the nozzle carrier and seals off the nozzle body against the nozzle carrier.
U.S. Pat. No. 4,313,570 describes a nozzle holder for a water jet cutting device wherein the nozzle body is surrounded by a ring of elastomeric material which is in turn mounted in a recess in the holder. The recess is in the form of a straight cylinder. The cross-section of the ring is rectangular. The outer surface of the recess and the outer and inner surfaces of the ring are arranged concentrically to the axis of the nozzle body and run parallel to one another and to the axis of the nozzle body.
WO 97/12683 discloses a device for clamping a fluidic component which is subjected to fluid pressure, which is suitable for components consisting of a wear-resistant, hard and hence generally brittle material, and which does not produce any excessively great local material tensions in the component. The fluidic component is arranged in a holder which makes contact with the fluidic component on its low pressure side. The fluidic component is surrounded by an elastomeric shaped part the outer contour of which is adapted to the inner contour of the holder and the inner contour of which is adapted to the outer contour of the fluidic component. The elastomeric component surrounds the entire circumference of the fluidic component. At least one free surface of the elastomeric component is exposed to the pressurized fluid. The holder may have a projection on the inside underneath which the elastomeric shaped part is pushed. It has proved difficult to generate internal tension in the elastomeric shaped part which is sufficiently great, even at low fluid pressures, and which is spatially roughly uniformly distributed in the elastomeric shaped part.
This known device has proved pressure-tight when subjected substantially constantly to moderate and high fluid pressures. When subjected to alternating fluid pressures fluctuating between a high peak value and a very low value, the known device is in need of improvement for long-term use.
The problem thus arises of providing a device for clamping a fluidic component which is reliably leak-tight even when subjected to alternating loading from a sharply fluctuating fluid pressure in long-term use. The components needed should be cheap to manufacture and should also be capable of being assembled with relative ease.